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From: Thiago Adams <thiago.adams@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: question about linker
Date: Wed, 27 Nov 2024 08:08:34 -0300
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On 27/11/2024 07:36, Michael S wrote:
> On Tue, 26 Nov 2024 16:42:34 -0300
> Thiago Adams <thiago.adams@gmail.com> wrote:
>>
>>
>> Yes..I realized now I am wrong. Considering function calls uses
>> registers I think the old C model works only when passing everything
>> on stack.
>>
>>
> 
> "Old model" relies on programmer always using right types in the
> function call. F(0) call Bart's example would not work even for calling
> conventions in which both int and double passed on the same stack,
> because [in typical pre-64-bit calling conventions] they don't occupy
> the same space. For correct result you would have to write it as
> F((double)0) or F(0.0).
> 
> Alternatively "old model" could work when all things that are allowed
> to be passed as function parameters are of the same size. It seems,
> that's what they had in ancestors of C language and probably in very
> early versions of C as well. It was no longer a case in variant of the
> language described by 1st edition of K&R.
> 

I will write in my own words. Correct me if I make a mistake.

Without function prototypes, the compiler will use the types it has on 
the caller's side, possibly with integer promotions.

Calling a function with a double will assume the function is implemented 
receiving a double.
The function implementation will need to match these types.

With function prototypes, we can call a f(int i) with f(1.1) and then 
the caller side will convert before calling f.